Parametric loudspeaker systems are known that employ ultrasonic transducers for projecting ultrasonic carrier signals modulated with audio signals through the air for subsequent reproduction of the audio signals along a selected path of projection. A conventional parametric loudspeaker system can include a modulator for modulating an ultrasonic carrier signal with an audio signal, at least one driver amplifier for amplifying the modulated ultrasonic carrier signal, and one or more ultrasonic transducers for directing the amplified, modulated ultrasonic carrier signal through the air along the selected projection path. For example, each ultrasonic transducer can be a membrane transducer, such as an electrostatic transducer or a piezoelectric transducer, either ceramic or membrane-type. Due to the non-linear propagation characteristics of the air, the modulated ultrasonic carrier signal is demodulated as it passes through the air, thereby reproducing the audio signal along the selected projection path.
Amplifier design for such parametric loudspeaker systems can present unique challenges. Unlike traditional loudspeaker systems that are typically weakly inductive, parametric loudspeaker systems tend to be highly capacitive. Further, while traditional loudspeaker systems are typically current-driven, some parametric loudspeaker systems are voltage driven. Moreover, the frequency range for parametric loudspeaker systems tend to be far greater than that of traditional loudspeaker systems.